The present invention relates generally to rolling mills and, more particularly, to so-called plug mills which are used to form elongated tubular shapes, such as, for example, metal pipe. Plug mills are usually two high mills, that is to say, they have two vertically spaced work rolls. The work rolls have axially extending shafts which are journaled for rotation in bearings which, in turn, are mounted in roll chocks. The roll chocks are then mounted in the mill housing, all of which is well-known in the art. The work rolls of the plug mill each have one or more hemispherically shaped grooves circumferentially formed therearound which mate to form a circular cross section when the rolls are brought together and axially aligned in the mill housing. A tubular workpiece having a circular cross section is then passed through the mating grooves of the work rolls while a plug mandrel is positioned within the hollow, workpiece. The plug functions to counteract the external rolling forces of the grooved work rolls to provide the desired workpiece deformation/elongation and dimensions, all well-known in the art.
In preparation for start-up, after the grooved work rolls have been placed in the mill housing, it is sometimes necessary to axially move at least one of the roll chocks in order to properly align the roll grooves prior to commencing operation of the mill. Heretofore, axial adjustment of the grooved rolls in a plug mill has been accomplished by manipulation of one of the roll chocks through the use of shims and wedges. This adjustment operation has proved to be a time consuming and labor intensive task. Pinch points are also present in the mill which present potential hazards for the installation personnel.
The present invention is directed to a device for axially adjusting the bottom roll chock of a plug mill to provide fast, safe and efficient alignment of the roll grooves of the top and bottom work rolls. The roll adjustment device of the present invention further provides for controlled axial movement of the bottom work roll in two directions relative to the pass line of the mill to allow very accurate roll adjustment in a minimum amount of time and with the utmost safety.
Still further, the roll adjustment device of the invention is adapted to be easily installed on new or existing mills with relatively little capital expense.